1Department of Biological Science, Gachon University of Medicine and Science, Incheon 406-799, Republic of Korea2Department of Biomedical Engineering, Gachon University of Medicine and Science, Incheon 406-799, Republic of Korea3Department of Life Science, Dongguk University-Seoul, Seoul 100-715, Republic of Korea

Received 21 December 2010; Revised 23 February 2011; Accepted 2 April 2011